Nondestructive reading method for isotopic label

ABSTRACT

A nondestructive reading method for an isotopic label, capable of easily and quickly reading information on an isotopic label imparted to an article in advance without destroying the label, and a nondestructive reading-use isotopic label suitably using this method. In addition, information obtained by this nondestructive reading method is used to easily and quickly judge the authenticity of an article.

TECHNICAL FIELD

This invention relates to a method for reading an isotopic label whichhas been attached to an article beforehand and is difficult to forge andfalsify, a method for judging the authenticity of an article using theinformation obtained by the reading method, and an isotopic labeladapted for use in these methods.

TECHNICAL BACKGROUND

An anti-counterfeit method of articles has been proposed wherein asubstance that is so controlled as to have a content ratio of a stableisotope different from the natural isotopic abundance ratio is employedas a label. For instance, in Japanese Laid-open Patent ApplicationNo.H10-287075, assigned to the present applicant, it is proposed that alabel or code whose content ratio of ¹³C is made larger than a naturalisotopic value is used. In Japanese Laid-open Patent ApplicationNo.H11-316200, a method of identifying a vehicle or television receiversusceptible to theft is proposed, in which although the content ratio ofa stable isotope is not controlled, at least two types of substancesincluding carbon-cage molecules such as of C₆₀ or the like and asubstance having a characteristic spectrum such as a metallo-organicsoap are used as a label after control of a ratio and concentrations.However, the Japanese Laid-open Patent Application No. H11-316200 makeslittle mention of specific labeled substances, or any reading method isnot particularly proposed. The Japanese Laid-open Patent Application No.2000-43460, assigned to the present applicant, proposes the use of alabel or code made of C₆₀ wherein a content ratio of ¹³C is set at avalue different from the natural value in order that the difference indegree of splitting of a light absorption spectrum of C₆₀ is utilized.Although this code is very effective in anti-counterfeiting thereof,limitation is placed on the range of application when using C₆₀ alone.Accordingly, there is a demand for development of various types oflabeled substances.

Additionally, WO 97/43751 (U.S. Pat. No. 5,760,394) has proposed alabeling method using a substance wherein a stable isotope is controlledin content ratio thereof, and also a label. However, the measurement ofthe label and its identification are described in examples using onlyinductive couple plasma mass spectrometry (ICPMS) for the analysis.ICPMS is such that an element is quantitatively determined by measuringthe intensity of an emission line corresponding to a wavelength of aphoton which is discharged when a thermally excited atom or ion isreturned to a lower energy level. Hence, in order to carry out themeasurement using ICPMS, a solid or liquid sample has to be initiallydestroyed thereby causing free atoms to be generated. In this way, ICPMSrequires not only such a large-scale apparatus per se as a massspectrometer, but also the essential step of generating free atoms bydestroying a solid or liquid sample, thus presenting a serious problemin terms of usefulness.

It should be noted that with respect to the reading of the label,mention is made merely of a suitable means only at the Abstract of thepatent, and no other reading means is disclosed in the specificationonly with the statement concerning the above-mentioned ICPMS, and thatany disclosure is not found at all particularly with respect to anondestructive method. In addition, although the WO 97/43751 enumeratesa great number of elements that are able to change a content ratio of astable isotope for use as a label, how these elements are used asconstituent elements for what types of substances are not illustratedexcept that mention is made only of Nd₂O₃ and Dy₂O₃ in examples. In viewof this, it is nothing else that further studies and developments arenecessary with respect to how these elements are usable as constituentelements of what types of substances.

Accordingly, a difficulty is involved in the practical use of ICPMSwhich is based on the assumption that a sample is destroyed, i.e. alabel is destroyed as set out in the examples of WO 97/43751.Consequently, further studies and developments toward the practical useare necessary so that the information of a label can be obtained as itstands, if possible, or can be obtained nondestructively. Moreparticularly, the development of a technique is strongly desired thatthe label be not destroyed, but information thereof is read as it is,ensuring immediate application to judgment on the authenticity of anarticle.

The invention has been accomplished in order to solve the problemsinvolved in the prior art methods using an isotopic label and has forits object the provision of a method for readily and reliably reading anisotopic label, attached on an article beforehand, without destroyingthe label and a method for judging the authenticity of an article usingthe information obtained by the reading method, and also the provisionof a novel and useful isotopic label which is adapted for use in thereading and authenticity judging methods.

DISCLOSURE OF THE INVENTION

In the practice of the invention, an isotopic label is attached on anarticle beforehand. The isotopic label is made of substances which,respectively, have a plurality of stable isotopes of at least oneelement selected among elements constituting the substances, i.e. aconstituent element, and which include both a substance wherein at leastone stable isotope is so controlled that a content ratio thereof islower than the natural isotopic abundance ratio (although both are samestructurally, the content ratio of the stable isotope of the element isso controlled as to be not higher than the natural isotopic abundanceratio) and a substance wherein at least one stable isotope is socontrolled that a content ratio thereof not lower than the naturalisotopic abundance ratio (although both are structurally same, thecontent ratio of the stable isotope of the element is so controlled asto be not lower than the natural isotopic abundance ratio). Vibrationspectra of the substances differ from a vibration spectrum of asubstance having all content ratios of the stable isotopes of theconstituent elements are equal to the natural isotopic abundance ratios,respectively. The invention is also favorable for nondestructivelyreading and obtaining the vibration spectra of the substancesconstituting the isotopic label.

Further, in the practice of the invention, an isotopic label is attachedon an article beforehand wherein the isotopic label is made of asubstance which has at least two elements selected from hydrogen,carbon, nitrogen and oxygen as the constituent elements with each of thecontent ratios of stable isotopes thereof being controlled to bedifferent from the natural isotopic abundance ratio and which has avibration spectrum different from the vibration spectrum of thesubstance whose content ratios of stable isotopes of the constituentelements are, respectively, equal to the natural isotopic abundanceratios. The invention is also favorable for nondestructively reading andobtaining the vibration spectrum of the substance constituting theisotopic label. In this case, it is favorable that an element orelements other than the above-mentioned elements and constituting theisotopically labeled substance do not have stable isotopes. If the otherelements of the constituent elements of the isotopically labeledsubstance have stable isotopes, part of the effects expected from theelements whose the ratios of the stable isotopes have been controlledmay be counteracted.

In the present specification, the label attached on an articlebeforehand and made of such a substance or substances as set forthhereinabove is called “isotopic label”.

In the present invention, the information obtained according to thenondestructive reading method is utilized for a method of judging theauthenticity of an article. More particularly, as stated hereinabove,the invention is also favorable for obtaining a vibration spectrum orspectra of the substance constituting the isotopic labelnondestructively, and the thus obtained information is used tonondestructively judge the authenticity of the isotopic label-attachedarticle. The authenticity judging method is carried out by use of adevice of reading and obtaining vibration spectra, a device of readingan isotopic label through pattern recognition of data of vibrationspectra, and a device of judging the authenticity of an article. In thiscase, these devices may be worked by connection via a communicationnetwork. For the communication network, at least one of a telephonecommunication network, an internet and an intranet can be used.Moreover, in order to perform the nondestructive authenticity judgingmethod of an article, at least one of devices including a device ofobtaining vibration spectra, a device of reading an isotopic labelthrough pattern recognition of data of vibration spectra, and a deviceof judging the authenticity of an article may be controlled from aremote area, or control parameters may be designated from a remote area.

In addition, the invention provides isotopic labels of (1)˜(3) below fornondestructive reading, which are adapted for use in a nondestructivereading method of the above-stated isotopic label and a method forjudging the authenticity of an article.

(1) An isotopic label for nondestructive reading which is attached on anarticle beforehand, comprising substances constituting the isotopiclabel which, respectively, have at least one constituent element havinga plurality of stable isotopes, include both a substance wherein acontent ratio of at least one stable isotope of the constituent elementis not higher than a natural isotopic abundance ratio and anothersubstance wherein a content ratio of the stable isotope of theconstituent element is not lower than a natural isotopic abundanceratio, and have vibration spectra differ from the vibration spectrum ofthe substance whose content ratios of stable isotopes of the constituentelements are equal to the natural isotopic abundance ratios,respectively.

(2) An isotopic label for nondestructive reading which is attached on anarticle beforehand, comprising a substance constituting the isotopiclabel which has at least two elements of constituent elements selectedfrom hydrogen, carbon, nitrogen and oxygen with each of the contentratios of stable isotopes thereof controlled to be different from thenatural isotopic abundance ratio and has a vibration spectrum differentfrom the vibration spectrum of the substance whose content ratios ofstable isotopes of the constituent elements are equal to the naturalisotopic abundance ratios, respectively.

(3) An isotopic label for nondestructive reading which is attached on anarticle beforehand, comprising a substance constituting the isotopiclabel which has at least two elements of constituent elements selectedfrom hydrogen, carbon, nitrogen and oxygen with each of the contentratios of stable isotopes thereof controlled to be different from thenatural isotopic abundance ratio, wherein constituent elements otherthan hydrogen, carbon, nitrogen and oxygen are elements which has nostable isotopes and which has a vibration spectrum different from thevibration spectrum of the substance whose content ratios of stableisotopes of the constituent elements are equal to the natural isotopicabundance ratios, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an outline of light absorption spectra ofsubstances M1˜M3 (a principle of nondestructive reading of an isotopiclabel);

FIGS. 2(a) and 2(b) are a view showing examples of preliminarilyattaching isotopic labels on articles for the purpose ofanti-counterfeiting;

FIG. 3 a view showing an example where vibration spectra are obtained bya diffused reflection method using AOTF;

FIG. 4 is a view showing an example wherein vibration spectra areobtained by an attenuated total reflection method using AOTF;

FIG. 5 is a view showing an example wherein a beam emitted from asemiconductor laser is irradiated on a substance constituting anisotopic label to measure an absorption intensity, a transmissionintensity and a reflection intensity;

FIG. 6 is a view showing an example wherein light emitted from asemiconductor laser is irradiated on a substance constituting anisotopic label and Raman lines appearing in the resultant scatteredlight are detected with a light-receiving element to determine avibration spectrum from the wave number (wavelength) and intensitythereof;

FIG. 7 is a view showing the results of Example 1;

FIG. 8 is a view showing the results of Example 2;

FIG. 9 is a view showing the results of Example 3;

FIG. 10 is a view showing the results of Example 4;

FIG. 11 is a view showing the results of Example 5; and

FIG. 12 is a view showing an application of the invention to admissionauthentication using a communication network in Example 7.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

In the practice of the invention, an isotopic label is attached on anarticle beforehand wherein the isotopic label is made of substances thathave a plurality of stable isotopes of at least one element selectedamong constituent elements, include a substance in which at least onestable isotope is so controlled as to have a content ratio thereof isnot higher than a natural isotopic abundance and a substance in whichthe at least one stable isotope has a content ratio thereof not lowerthan the natural isotopic abundance, and are used in combination, andwherein vibration spectra of the substances differ from a vibrationspectrum of a substance having a content ratio of the stable isotope ofthe at least one element in coincidence with the natural isotopicabundance. The vibration spectra information of the labeled substancesis nondestructively read and obtained as it is.

It should be noted here that both substances, i.e. a substance which hasa plurality of stable isotopes with respect to at least one ofconstituent elements for the substance and has a controlled contentratio of at least one stable isotope thereof not higher than a naturalisotopic abundance and a substance which has a controlled content ratioof the stable isotope not lower than the natural isotopic abundance, arestructurally similar to each other and, respectively, have a contentratio of the stable isotope of the element different from the naturalisotopic abundance.

It will be noted that the use, as a label, of a substance of the typewherein the constituent element of the isotopic label-constitutingsubstance is carbon and the content ratio of ¹³C is made larger than anatural value has been already developed (Japanese Laid-open PatentApplication No. H10-287075). In contrast, according to the invention, inaddition to a substance whose content ratio of ¹³C is larger than anatural value, a substance whose content ratio of the stable isotope isnot higher than a natural isotopic abundance is used in combination asstated hereinabove. This makes counterfeiting more difficult and canfurther increase a security level.

In the practice of the invention, a label made of an isotopic labelconstituting substance is attached on an article beforehand whereinconstituent elements for the substance include at least two elementsselected from hydrogen, carbon, nitrogen and oxygen, and the at leasttwo elements are so controlled as to have content ratios of stableisotopes thereof different from natural isotopic abundances,respectively, so that the vibration spectrum thereof is made differentfrom a vibration spectrum of a substance having content ratios of stableisotopes of these elements in coincidence with natural isotopicabundances. The vibration spectrum information of the isotopicallylabeled substance is read and obtained as it is, i.e., nondestructively.

In the case, when elements other than the above-indicated elements amongthe constituent elements of the isotopically labeled substance havestable isotopes, part of the effects expected from the elements whichare controlled in the stable isotope ratio may be counteracted. In thissense, it is desirable that elements other than the above-mentionedconstituent elements of the isotopically labeled substance do not haveany stable isotope. Examples of the elements having no stable isotopeinclude Be, F, Na, Al, P, Sc, Mn, Co, As, Y, Nb, Rh, I, Cs, Pr, Tb, Ho,Tm, Au, Bi, Th and the like.

In the practice of the invention, a vibration spectrum of a substanceconstituting an isotopic label is nondestructively obtained in a manneras set out hereinbefore, and the authenticity of the isotopiclabel-attached article is nondestructively judged based on the thusobtained information. Different types of isotopic labels made of suchmaterials as described hereinabove may be built up in multiple layersand attached on the same portion of an article. Light is irradiated onthe substances constituting the isotopic labels to identify the isotopiclabels from the intensity of reflected light, of transmitted light or ofscattered light thereby reading information thereof. In this way, theinformation of the isotopic labels can be utilized in high accuracy andquickly. In case where the invention is applied to the inspection of ananti-counterfeit, the information of the preliminarily attached isotopiclabel as set out before proves the article as authentic. If theinformation is not obtained, the article is judged as a counterfeit.

Thus, according to the invention, vibration spectra of an isotopic labelcan be read and obtained readily and accurately without destroying asample or the isotopic label while permitting the isotopic label tostand, and the judgment of authenticity of an article attached with anisotopic label thereon can be made nondestructively, readily andaccurately. In this regard, in the afore-indicated ICPMS (WO 97/43751),the step of destroying a solid or liquid sample, or an isotopic label tocause free atoms to be generated is essential, and such a large-scaleapparatus as a mass spectroscope per se is necessary. According to theinvention, the information on an isotopic label can be readnondestructively, readily and accurately, thus being very effective anduseful from the standpoint of practical use.

Principle of Nondestructive Reading of an Isotopic Label

When light is irradiated on a substance to measure a ratio of absorbedlight, the absorption ratio differs depending the energy of theirradiating light. The absorption ratio may be expressed by eitherabsorbance or absorption intensity, and is illustrated in terms ofabsorbance hereinbelow. The results of the measurement are shown by agraph wherein the abscissa indicates a wave number or wavelength ofirradiating light and the ordinate indicates an absorbance. This curveis called light absorption spectrum of the substance. The lighttransmittance spectrum or light reflection spectrum obtained bymeasuring a transmittance or reflectance in place of absorbancedescribes a light absorption spectrum-related curve, and thusillustration is made herein using the term of the light absorptionspectrum on behalf of spectra including the last-mentioned ones.

In the light absorption spectrum, the reason why light is stronglyabsorbed at a specific energy (or at a specific wave number or specificwavelength) corresponding to a peak position is that when the energylevel of an atom or molecule constituting a given substance istransferred to a higher level, an absorbed energy takes only a specificvalue.

With a molecule made of a plurality of atoms, vibrations take placebetween the atoms. The vibration energy of the molecule ascribed to thevibrations may take a specific value alone that is determined dependingon the masses of individual atoms and the bonding force between theatoms. If a vibration state changes depending on the absorption oflight, the value of the vibration energy changes. A possible value ofthe vibration energy is determined depending on the combination ofvibrating atoms, and the energy of the light absorbed upon the change ofthe vibration energy is limited to a specific value.

Of light absorption spectra of a substance, a portion formed as a resultof the change in vibration state between the constituent atoms is calledvibration spectrum of the substance. The range of the irradiation lightenergy within which a vibration spectrum appears is usually limited to aportion called infrared region. The infrared region used herein is ageneral term for near infrared region, mid infrared region, and farinfrared region. The light absorption spectrum is usually inherent to agiven substance.

By the way, an isotope means the forms of an element having differentatomic weights because of the difference in number of neutrons. Amongisotopes, a stable isotope does not have radioactivity and is a stableone undergoing no decay. In a natural condition, the relative isotopicabundance ratio of individual elements is constant. For instance, carbonincludes two isotopes of ¹²C and ¹³C and it is known that the naturalisotopic abundance ratio of these isotopes is at 98.89:1.11. Moreparticularly, with a substance wherein a content ratio of stableisotopes in an element constituting a substance having carbon as aconstituent element is at the natural isotopic abundance ratio, thecontent ratio of ¹²C relative to the total carbon content is at 98.89%and the content ratio of ¹³C is at 1.11%.

The light absorption spectrum is usually inherent to a given substance,and the vibration energy between the constituent atoms of a substancedepends on the masses of the atoms. The mass of an atom differs betweenthe isotopes thereof. Accordingly, with a substance whose constituentelement has stable isotopes, the content ratio of the stable isotopesinfluences the vibration spectrum. More particularly, the difference ofthe stable isotope content ratio of the constituent element of asubstance from the natural isotopic abundance ratio results in thedifference of the vibration spectrum.

In accordance with the invention, this phenomenon is utilized fornondestructive reading of an isotopic label. It will be noted that amonglight absorption spectra, a portion other than irradiation light where avibration spectrum appears, such as a portion corresponding to a visibleregion, suffers little influence of the content ratio of stableisotopes.

For example, it is assumed that element X has two types of stableisotopes X1, X2 alone and substance M makes use of this element X as oneof constituent elements thereof. The content ratios of stable isotopesof the constituent elements other than the constituent element X arecoincident with natural isotopic abundance ratios, respectively. In thiscondition, a substance wherein the content ratio of the stable isotopeX1 of the constituent element X is much higher than the content ratio ofthe isotope X2 is taken as M1, a substance wherein the content ratio ofthe stable isotope X1 of the constituent element X is much lower thanthe content ratio of the isotope X2 is taken as M2, and a substance madeof a mixture of the substances M1 and M2 substantially in equal amountsis taken as M3.

In some case, the influence of the content ratio of these stableisotopes may clearly appear at part of the vibration spectra of thesethree kinds of substances M1, M2 and M3. FIG. 1 is a view showing theoutlines of the light absorption spectra of the substances M1, M2 andM3, respectively. Since the content ratios of the stable isotopes of theelement X constituting the molecule are different between the substancesM1 and M2, a difference appears in the peak position within a wavenumber region 1 of the light absorption spectra shown in (a) and (b).With the light absorption spectrum (c) of the substance M3, a M-shapedpeak appears as a result of the superposition of both peaks. When thelight absorption spectrum at the wave number region is obtained, thesubstances M1˜M3 can be identified, respectively. Depending on whetherthe ordinate of the graph is taken as an absorbance (absorptionintensity) or as a transmittance (transmission intensity), the M-shapedpeak may appear for the absorption intensity and the W-shaped peakappears for the transmission intensity. In this way, the substancesM1˜M3 can be, respectively, identified by obtaining light absorptionspectra or light transmission spectra in the wave number region 1. Itwill be noted that the light absorption spectra in the wave numberregion 2 of FIG. 1 are common to the substances M1˜M3.

If the state where the content ratio of the stable isotopes in theconstituent element of the substance M is at the natural isotopicabundance is close to that of the substance M1, the other two types ofsubstances M2, M3 cannot be obtained unless they are artificiallysynthesized by use of rare stable isotopes. Thus, these substances haverarity. When a label is constituted by use of such highly raresubstances, it is realized to provide a label which is difficult toforge and is high in security level.

The case where the element X has two -types of stable isotopes X1, X2has been illustrated hereinabove, which is true of the case whereelement X has three or more types of stable isotopes X1, X2, X3, . . . .In addition, it has been illustrated above that the content ratio of thestable isotopes of only one element X of constituent elements of asubstance is controlled. The content ratios of stable isotopes of two ormore, or at least two, elements selected among a plurality ofconstituent elements of a substance, such as hydrogen, carbon, nitrogen,oxygen and the like, may be controlled in a like manner. Moreover, withrespect to at least two elements selected among a plurality ofconstituent elements of a substance, such as hydrogen, carbon, nitrogen,oxygen and the like, the stable isotope content ratios of the pluraltypes of elements in the molecule of the substance may be likewisecontrolled, respectively.

FIGS. 2(a) and 2(b) show an instance of attaching an isotopic label onan article beforehand for the purpose of anti-counterfeiting. In FIGS.2(a) and 2(b), an isotopic label is indicated as a code herein andwhenever it appears hereinafter in the drawings. In FIG. 2(b) shows aninstance of an isotopic label where isotopic label-attaching spots aretwo-dimensionally arranged, i.e., an instance of attaching an isotopiclabel wherein 16 spots are attached with or not attached with any ofsubstances M1˜M3. When information is expressed in terms of whether anyof the substances M1, M2 and M3 used for the isotopic label is attachedto a spot or no substance is attached to the spot, four pieces ofinformation per spot may be coded. Because any one of the four pieces ofinformation can be assigned to one spot, the use of a label consistingof a substance controlled in the content ratio of the stable isotope atat least one spot enables one to express 4^16−2^16=about 4.29 billionsof pieces of information. According to this procedure, a label which isdifficult to forge and has a high information recording density can berealized.

Nondestructive Reading Means of an Isotopic Label

In the practice of the invention, information on an isotopic label isnondestructively read by obtaining a vibration spectrum of a substanceconstituting the isotopic label. For the reading, an infrared absorptionmethod or a Raman scattering method is conveniently used.

In the infrared absorption method, an infrared ray is irradiated on asubstance constituting an isotopic label and the intensity of reflectedlight, transmitted light or scattered light is detected by means of alight-receiving element to obtain a vibration spectrum of the substancefor the isotopic label. The vibration spectrum can be obtained by adiffuse reflection method, an attenuated total reflection method (ATRmethod), photoacoustic spectrometry and the like, which are ordinarily,widely employed IR absorption methods.

In the Raman scattering method, monochromatic light is irradiated on asubstance for an isotopic label and the resultant Raman line appearingin the scattered light is detected by a light-receiving element toobtain a vibration spectrum of the substance of the isotopic label fromthe wave number (wavelength) or intensity.

When using a device of obtaining the vibration spectrum, various controlparameters including the position of the isotopic label to be read on anarticle, the range of a wave number at which the vibration spectrum isto be obtained, and the like can be set appropriately.

Where the invention is applied to the judgment of the authenticity of anarticle (see Example 7), a smaller-size vibration spectrum-obtainingdevice is convenient for the purpose of accommodation and portability.In this case, it is favorable to use as a light source for irradiationlight a device capable of conversion of continuous light intomonochromatic light through an acousto-optic tunable filer (abbreviatedas AOTF) or a semiconductor laser.

When using AOTF, monochromatic light within a wide range of wave number(wavelength) can be created without any movable parts, so that thevibration spectrum-obtaining device can be made small in size and lightin weight. FIG. 3 shows an instance where vibration spectra are obtainedby a diffuse reflection method using AOTF. FIG. 4 shows an instancewhere vibration spectra are obtained by an attenuated total reflectionmethod using AOTF.

When using a semiconductor laser, monochromatic light can be created byuse of a very small-sized light source. In order to obtain one peak (orvalley) in the vibration spectrum, it becomes necessary to obtainspectral information with respect to three wave numbers (wavelengths) atwhich the intensity changes as being low→high→low (or high→low→high). Inthe infrared absorption method, as shown in FIG. 5, the light generatedby a semiconductor laser is irradiated on a substance for a label tomeasure an absorption intensity, a transmission intensity or areflection intensity. The wave number (wavelength) of the beam obtainedfrom a light source using a semiconductor laser can be changed within aspecified range by controlling the temperature of the semiconductorlaser or an inputted current value, or by using an external resonator.This enables one to obtain at least one peak in the vibration spectrumby use of a semiconductor laser. In the Raman scattering method, asshown in FIG. 6, the beam generated by a semiconductor laser isirradiated on a substance for an isotopic label and a Raman lineappearing in the resulting scattered light is detected by means of alight-receiving element to obtain a vibration spectrum from the wavenumber (wavelength) or intensity.

Although information concerning a content ratio of a stable isotope inthe constituent element of a substance is obtained by obtaining avibration spectrum of the substance for an isotopic label, informationconcerning the color of the substance can be obtained by obtaining alight absorption spectrum of the substance within a visible region.Using both pieces of information, the substance for an isotopic label isidentified, thereby improving the reliability of the identification,thus enabling the isotopic label to maximize its latent security level.

When using substances such as dyes which have the same color but aredifferent in the content ratio of stable isotopes, it becomes possibleto provide isotopic labels which are difficult to discriminate throughvisual observation. In this connection, however, the discriminationthrough visual observation is not performed with the unmanned orunattended case such as of a vending machine. If a label is read onlyfrom a vibration spectrum, isotopic labels which have the same vibrationspectrum but are different in color cannot be discriminated from eachother. In the unmanned case, the high latent security level of theisotopic label can be shown through visual observation while getting alight absorption spectrum in the visible region, which plays the rolesimilarly.

With the IR absorption method using a semiconductor laser, at leastthree kinds of light whose wavelengths are both in the infrared regionand in the visible region generated by use of at least two semiconductorlasers are utilized and at least one peak in each of a vibrationspectrum in the infrared region and a light absorption spectrum in thevisible region is obtained. Where the wave number region 1 of theafore-indicated FIG. 1 is part of the vibration spectrum and the wavenumber region 2 is part of the light absorption spectrum in the visibleregion, the wave numbers of the light generated by the two semiconductorlasers are made in coincidence with the wave number regions 1 and 2,respectively, thereby enabling the substances having the lightabsorption spectra (a)˜(c) in FIG. 1 to be identified from one another.Using information concerning at least one peak obtained in each of bothregions, substances for the isotopic label are identified, respectively.

With the Raman scattering method, in addition to the vibration spectrumbeing obtained by detecting a Raman line by use of a semiconductor laserhaving a wave number (wavelength) in the visible region as anirradiation light source, at least three kinds of light having differentwave numbers (wavelengths) are generated by the use of the semiconductorlaser, and the beams are irradiated on the substances for an isotopiclabel to measure the intensity of transmitted light, scattered light orreflected light, thereby obtaining at least one peak of the lightabsorption spectrum in the visible region. Using information concerningthe resulting vibration spectrum and the at least one peak of the lightabsorption spectrum in the visible region, a substance for the isotopiclabel is identified.

Next, the thus obtained vibration spectrum is subjected to patternrecognition or is compared with a reference data by use of an isotopiclabel reader and is thus identified to read the isotopic label. The dataof the obtained vibration spectra may be subjected to patternrecognition by use of the discrimination model prepared according tochemometrics. It will be noted that the term “chemometrics” is a newlycoined word from the combination of chemistry and metrics, and is atechnique which makes full use of mathematical and statisticaltechniques to maximize the amount of chemical information extracted fromchemical data such as vibration spectra.

For the preparation of the discrimination model, a data set of amultitude of samples whose classes to be sorted have been identifiedbeforehand is used. The wave number of vibration spectrum is taken as anexplaining variable and the strength is taken as its value, and adiscrimination model in a technique such as KNN (K nearest neighbor) orSIMCA (soft independent modeling of class analogy) or the like isconstructed and optimized. Using such a discrimination model as preparedbeforehand, the class of an actually obtained vibration spectrum can beidentified or sorted.

It will be noted that a method of identifying a printed matter has beenalready proposed (Japanese Laid-open Patent Application No. H10-149473),in which a resin or pigment forming a printed matter is identified byuse of a slight difference in near infrared spectrum. In the inventionof the Japanese Laid-open Patent Application No. H10-149473, a slightdifference in the vibration spectrum of a material used is utilized. Incontrast, according to the invention, a material having a specificvibration spectrum is positively used as a label, thereby ensuringreliable construction of a discrimination model of a higherdiscrimination or identification capacity.

Preferred Examples of Isotopically Labeling Substances forNondestructive Reading

In the practice of the invention, an isotopic label for nondestructivereading is attached to an article beforehand. The preferred substancesof the invention constituting the isotopic label for nondestructivereading should contain at least one element having a plurality of stableisotopes, should include one substance wherein a content ratio of atleast one stable isotope of the plural isotopes is so controlled as tobe not higher than a natural isotopic abundance ratio and anothersubstance wherein a content ratio of the stable isotope is so controlledas to be not lower than the natural isotopic abundance ratio, and shouldhave a vibration spectrum which differs from the vibration spectrum ofthe substance having a content ratio of the stable isotope of theconstituent element equal to the natural isotopic abundance ratio. Bothsubstances, i.e. a substance containing at least one stable isotopehaving a plurality of stable isotopes with a content ratio of at leastone stable isotope selected there among being not higher than thenatural isotopic abundance ratio and a substance wherein the contentratio of the stable isotope is not lower than the natural isotopicabundance ratio, are same in the chemical structure thereof but have thecontent ratios of the stable isotope of the element which, respectively,differ from the natural isotopic abundance ratios. Both are applied toby an appropriate technique including (1) attachment to an article as amixture, and (2) attachment of either of them to an article and theother put thereon.

Other preferred substances constituting the isotopic label fornondestructive reading are those substances wherein with respect to atleast two elements selected from hydrogen, carbon, nitrogen and oxygen,the content ratios of the stable isotopes thereof are so controlled asto differ from natural isotopic abundance ratios, respectively, andvibration spectra differ from a vibration spectrum of a substance havingcontent ratios of the stable isotopes of the constituent elements equalto the natural isotopic abundance ratios, respectively. In thisconnection, it is preferred that the substances should not have stableisotopes in constituent elements other than hydrogen, carbon, nitrogenand oxygen. As having stated hereinbefore, if elements other than thespecified elements of a labeling substance have stable isotopes, part ofthe effect expected from the elements whose ratios of stable isotopesare controlled may be counteracted in some case.

Preferred examples of the substance of the isotopic label are thosesubstances which are in the form of a stable solid at normal temperatureand normal pressure. Examples include urea, glycine, leucine, alanine,glucose, ammonium nitrate, ammonium acetate, ammonium phosphate, sodiumphosphate, benzamide, sodium nitrate, diphenyl, dicyclohexane, benzoicacid, sodium acetate, sodium carbonate, sodium hydrogencarbonate, sodiumpropionate, sodium formate, sodium octanoate, sodium glutamate,phthalimide, valine, sodium octanoate, sodium palmitate and the like.

Other preferred examples of the substance for the isotopic label includedyes. The dye used herein should be broadly interpreted and meanspigments and dyestuffs included within the category thereof. Those dyesare preferably used, in which a light absorption spectrum in the visibleregion is equal to that of a dye having content ratios of stableisotopes in elements equal to the natural isotopic abundance ratios (asstated hereinbefore, the vibration spectrum obtained by irradiation oflight in the visible region suffers little influence of the contentratio of a stable isotope), but a vibration spectrum in the infraredregion differs from that of a dye wherein content ratios of stableisotopes in elements are equal to the natural isotopic abundance ratios.Examples of the dye include phthalocyanine, indigo, aniline black,magenta, methyl violet, azo methine, quinacridone, and the like.

Applications of an Isotopic Label for Nondestructive Reading

The purposes in end use of an isotopic label according to the inventioninclude, aside from (1) the judgment of authenticity, (2)identification, (3) quality certificate, (4) copyright protection, (5)determination of a stolen article, (6) logistics, (7) stock control, andthe like. The label used herein means one which is attached to for thepurposes of (1)˜(7) above and allied purposes. More particularly,according to the invention, the isotopic label can be widely used in thefields where it is attached to an article and its information is read.Accordingly, the article attached with the isotopic label of theinvention is not limited so far as the attachment of the label isnecessary for these purposes. Although mutually overlapped examples maybe mentioned because of the classification based on the purpose orshape, examples of (1)˜(6) below can be indicated.

(1) For exchange tickets, paper currency, stamp, postage stamp, exchangecoupon, bond, stock, bill, check, security or policy, book coupon andthe like, (2) for brand name goods, bags, ornamental articles, articlesof clothing, watches or clocks, rings, necklaces, cars and the like, (3)for objects for copyright protection, CD, optical disk, software forcomputer and the like, (4) for jewelry and noble metals, coin, noblemetal bullion, badge of company, tag, picture, fine art, used item ofprominent figure, medicine and the like, (5) for sheets, passport,various licenses, ID card, name card, ticket for spectator sports,ticket for theatre, prescription, medical certificate, inspection tag,official document and the like, and (6) for cards, credit card,telephone card, ticket or card used in mass transit such as by railwayor bus, highway card, card for pachinko and the like software-built incards, and the like.

The type of material for the sheets per se is not limited and hard paperand the like various types of paper are ordinarily used along withplastics. The type of material for the cards per se is not limited, andvarious types of materials may be used including, aside from syntheticresins such as acrylic resins, polyester resins, polyolefin resins(including polyvinyl chloride and the like), polyamide resins,polyurethane resins, polycarbonate resins and the like, metals such asaluminium (including alloys thereof), paper and the like.

EXAMPLES

The invention is described in more detail by way of examples includingapplications thereof, which should not be construed as limiting theinvention thereto. In the following, the symbols of M, M1˜M3, and theM-shaped form indicated in “Principle of nondestructive reading ofisotopic label” are used for illustration.

Example 1

This example is one wherein sodium formate (HCOONa) was used assubstance M constituting an isotopic label. Among the constituentelements of sodium formate, carbon C has two types of stable isotopes of¹²C and ¹³C. By synthesizing “substances wherein the content ratios ofstable isotopes of constituent elements other than carbon are equal tothe natural isotopic abundance ratios, respectively, and the contentratios of the stable isotopes alone of carbon are appropriatelycontrolled”, sodium formate substances corresponding to the substancesM1˜M3, respectively, can be obtained. Sodium formate having a stableisotope ratio corresponding to the natural isotopic abundance ratio wasused as a substance corresponding to substance M1. Artificiallysynthesized sodium formate wherein a content ratio of ¹²C is at 1% wasprovided as one corresponding to substance M2, i.e. sodium formatewherein the content ratio of ¹²C is significantly lower than the contentratio of ¹³C. Sodium formate which consists of a mixture of M1 and M2 inequal amounts (by weight) was provided as one corresponding to substanceM3. It will be noted that among the constituent elements of thesubstance, Na is an element having no stable isotope.

The powders of the three types of sodium formate were each diluted witha potassium bromide powder to 5 wt %, and each was applied onto thesurface of a plastic card (vinyl chloride resin), followed by coverageof the surface with a silicon thin sheet and measurement of a vibrationspectrum according to a diffuse reflection method. FIGS. 7(a)˜(c) are,respectively, a view showing part of the results based on the actualmeasurements. In FIG. 7, peaks indicted by the arrows (↓) differ fromone another. As shown in FIG. 7(c), with the mixture in equal amountscorresponding to substance M3, a M-shaped spectrum is contained. In thisway, three types of sodium formate can be distinctly discriminated fromone another by measuring vibration spectra within a specific wave numberregion (wavelength region), and can thus be used as a constituentsubstance of an isotopic label carrying information, respectively. Inwave number regions other than those shown in FIGS. 7(a)˜(c), six ormore peaks which can be used for the discrimination can be confirmed.

Therefore, as for sodium formate, the form of sodium formate with thenatural isotopic abundance ratio of carbon is close to one correspondingto substance M1, and thus those forms corresponding to substances M2 andM3 have high rarity and can be used as constituent substances forisotopic labels that are difficult to forge.

FIG. 7(d) shows the results of measurement of a vibration spectrum ofsodium formate of the type wherein the ratio of the stable isotopes ofhydrogen was controlled at ¹H:²H (²H=D)=1:99 and the content ratios ofstable isotopes of the constituent elements other than hydrogen werecoincident with the natural isotopic abundance ratios, respectively. Thesodium formate of FIG. 7(a) has the natural isotopic abundance ratio ofhydrogen, ¹H:²H (²H=D)=99.985:0.015, and the peaks of FIGS. 7(a) and(d), indicated by the arrows, differ from each other. Thus, the twotypes of sodium formate can be distinctly discriminated from each otherby measuring the vibration spectra within the specific wave numberregion (wavelength region) and can be used as constituent substances forinformation-carrying labels, respectively.

Example 2

Two types of sodium formate, each controlled in a content ratio ofstable isotopes, (both were solid at normal temperature and normalpressure and were used as a powder in this experiment), and a mixture ofthe two types of sodium formate were, respectively, subjected tonondestructive measurement of a vibration spectrum in near infraredregion by using an infrared absorption method with an acousto-opticaltunable filter. FIG. 8 is a view showing the results of the measurementwherein the vertical axis shows light absorption intensity (arbitraryunit=A.U.) and the horizontal axis shows wavelength. In FIG. 8,(a)indicates a light absorption spectrum of sodium formate (represented byDCOONa) wherein the content ratio of stable isotopes of hydrogen wascontrolled to be ¹H:²H (²H=D)=1:99, (b) indicates a light absorptionspectrum of sodium formate (represented by H¹³COONa) wherein the contentratio of stable isotopes of carbon was controlled to be ¹²C:¹³C=1:99,and (c) indicates a light absorption spectrum of a mixture containing 88wt % of DCOONa and 12 wt % of H¹³COONa. As shown in FIGS. 8(a)˜(c), thelight absorption spectrum (c) of the mixture of the two types of sodiumformate, i.e. a mixture of two types of sodium formate wherein thecontent ratios of the stable isotopes of hydrogen and carbon are,respectively, controlled, apparently differs from those of sodiumformate (a) and (b) wherein the content ratio of stable isotopes of onetype of element is controlled. In FIG. 8, the portion indicated by thearrow (↓) indicates the afore-mentioned, artificially introducedM-shaped light absorption spectrum. This mixture is more rare than thesubstance wherein the content of stable isotopes of one type of elementsis controlled and can be used as a constituent substance for isotopiclabels that is more difficult to forge.

Example 3

Sodium formate wherein the content ratio of stable isotopes of hydrogenwas controlled, sodium formate wherein the content ratio of stableisotopes of carbon was controlled (both were solid at normal temperatureand normal pressure and were used as a powder in this experiment,respectively), and a mixture of these two types of sodium formate wereeach subjected to nondestructive measurement of a vibration spectrum byusing a Raman scattering method. FIG. 9 is a view showing the resultswherein the vertical axis shows scattered light intensity (arbitraryunit=A.U.) and horizontal axis shows Raman shift. In FIG. 9,(a)indicates the scattered light intensity of sodium formate (indicated bynatHCOONa) with the natural isotopic abundance ratios, (b) indicates ascattered light intensity of sodium formate (indicated by DCOONa)wherein the content ratio of stable isotopes of hydrogen is controlledsuch that ¹H:²H (²H=D)=1:99, (c) indicates the scattered light intensityof sodium formate (indicated by H¹³COONa) wherein the content ratio ofstable isotopes of carbon is controlled to be ¹²C:¹³C=1:99, and (d)indicates the scattered light intensity of a mixture of 50 wt % of theDCOONa and 50 wt % of the H¹³COONa.

As shown in FIGS. 9(a)˜(d), the Raman spectrum (d) of the mixture of thetwo types of sodium formate, i.e. a mixture of two types of sodiumformate wherein the content ratios of stable isotopes of hydrogen andcarbon are, respectively, controlled, apparently differs from thoseRaman spectra (a)˜(c) of the other three types of sodium formate. InFIG. 9, the artificially introduced M-shaped Raman spectrum appears atthe portion indicated by the arrow (↓). The mixture is more rare thanthe other three substances and can be used as a constituent substancefor isotopic labels that are more difficult to forge.

Example 4

In this example, sodium acetate substances wherein the content ratios oftwo stable isotopes of each of hydrogen and carbon were controlled (bothwere solid at normal temperature and normal pressure and were used as apowder in this experiment) were used as constituent substance of anisotopic label of the invention and were subjected to nondestructivemeasurement of a light absorption spectrum in near infrared region byusing an infrared absorption method with an acousto-optic tunablefilter. FIG. 10 is a view showing the results of the measurement whereinthe vertical axis shows light absorption intensity (arbitrary unit=A.U.)and the horizontal axis shows wavelength. In FIG. 10,(a) indicates alight absorption spectrum of sodium acetate (indicated by CD₃ ¹³COONa)wherein the content ratio of stable isotopes of hydrogen was controlledto be ¹H:²H (²H=D)=1:99 and the content ratio of stable isotopes ofcarbon was controlled to be ¹²C:¹³C=1:99. (b) indicates a lightabsorption spectrum of sodium acetate (CD₃COONa) wherein the contentratio of stable isotopes of hydrogen was controlled to be ¹H:²H(²H=D)=1:99. (c) indicates a light absorption spectrum of sodium acetate(CH₃ ¹³COONa) wherein the content ratio of stable isotopes of carbon wascontrolled to be ¹²C:¹³C=1:99.

As shown in FIGS. 10(a)˜(c), the light absorption spectrum (a) of sodiumacetate (CH₃ ¹³COONa) wherein the content ratios of stable isotopes ofboth of hydrogen and carbon were controlled apparently differs fromthose light absorption spectra (b) and (c) of the sodium acetatesubstances wherein the content ratio of stable isotopes of either ofhydrogen or carbon was controlled. In FIG. 10, the portion indicated bythe arrow (↑) is the afore-mentioned artificially introduced M-shapedlight absorption spectrum. This substance can be used as a constituentsubstance for isotopic labels which has more rarity and are moredifficult to forge.

Example 5

This example illustrates the use of urea [CO(NH₂)₂] as substance M forisotopic labels. Among the constituent elements of urea, hydrogen H hastwo types of stable isotopes of ¹H and ²H, with the natural isotopicabundance thereof being at 99.985% for ¹H and at 0.015% for ²H (=D).When “a substance wherein the isotopic content ratios of the constituentelements other than hydrogen are, respectively, equal to the naturalisotopic abundances and only the isotopic content ratio of hydrogen iscontrolled”, i.e. urea wherein only the isotopic content ratio ofhydrogen differs from the natural isotopic abundance ratio (or iscontrolled), is synthesized, urea substances corresponding to theafore-indicated M1˜M3 can be obtained. For substance M1, urea of thetype wherein the content ratio of ¹H is significantly higher than thecontent ratio of ²H is used. For substance M2, urea of the type whereinthe content ratio of ¹H is significantly lower than the content ratio of²H is used. For substance M3, a urea mixture of these substancessubstantially in equal amounts is used. This means that the natural formof urea is close to that corresponding to substance M1, and thosesubstances corresponding to substances M2 and M3, respectively, havehigh rarity and can be used as constituent substances for isotopiclabels that is difficult to forge.

Among the constituent elements of urea, nitrogen N has two types ofstable isotopes of ¹⁴N and ¹⁵N, with their natural isotopic abundancebeing at 99.63% for ¹⁴N and at 0.366% for ¹⁵N. By synthesizing “asubstance wherein the isotopic content ratios of the constituentelements other than nitrogen are, respectively, equal to the naturalisotopic abundance ratios and only the isotopic content ratio ofnitrogen is controlled”, i.e. urea wherein only the isotopic contentratio of nitrogen differs from the natural isotopic abundance ratio,urea substances corresponding to substances M1˜M3 can be obtained, likethe case of hydrogen. Moreover, with respect to carbon C selected amongthe constituent elements of urea, urea substances corresponding tosubstances M1˜M3 can be obtained in a similar way.

FIG. 11 is a view showing part of a vibration spectrum of each of thefollowing samples (a)˜(e), wherein about 2 mg of individual samples wasattached to an aluminium sheet, covered with a silicon thin sheet andsubjected to a diffuse reflection method to obtain a vibration spectrumbased on the resultant actual measurement. In FIG. 11, the vertical axisshows light absorption intensity [arbitrary unit=A.U.] and thehorizontal axis shows wave number.

-   -   (a) Urea having the natural isotopic abundance ratios.    -   (b) A sample obtained by diluting artificially synthesized urea,        which has a content ratio of ¹²C of 1% considerably lower than        the content ratio of ¹³C, with powders of potassium bromide to 5        wt %.    -   (c) A mixture sample obtained by mixing (a) and (b) above in        equal amounts (by weight).    -   (d) A sample obtained by diluting artificially synthesized urea,        which has a content ratio of ¹⁴N of 1% considerably lower than        the content ratio of ¹⁵N, with powders of potassium bromide to 5        wt %.    -   (e) A sample obtained by diluting artificially synthesized urea,        which has a content ratio of ¹H of 1% considerably lower than        the content ratio of ²H, with powders of potassium bromide to 5        wt %.

As shown in FIGS. 11(a)˜(e), the peaks indicated by the respectivearrows (↓) differ from one another. When the vibration spectra withinthe respective wave number regions (wavelength regions) including thesepeaks are obtained, these substances can be discriminated from oneanother. Within wave number regions other than the regions indicated inFIG. 11, five or more peaks which could be used for the discriminationwere confirmed.

An artificially formed M-shaped peak appears at the portion indicated bythe arrow (↓) of FIG. 11(c). It will be noted that with respect to FIG.11, a technique using a label code wherein the content ratio of ¹³C ishigher than the natural abundance ratio has been already developed(Japanese Laid-open Patent Application No.H10-287075). In the practiceof the invention, the artificial realization of the M-shaped vibrationspectrum ensures the provision of an isotopic label which is difficultto forge and exhibits a higher security level.

Example 6

This example illustrates an instance wherein in (a) of FIG. 2 showingthe attachment of an isotopic label, the dye used at character A is madeof a dye whose light absorption spectrum in the visible region is equalto that of a natural dye but differs from that of the natural dye withrespect to the vibration spectrum in the infrared region, and thenatural dye is used at characters B, C. The character portion of A andthe character portions of B, C seem to have the same color throughvisual observation. However, when vibration spectra in the infraredregion are obtained, the true isotopic label indicates that thevibration spectrum of the character portion of A alone is different fromthat of the natural dye.

As stated hereinabove, a dye wherein the content ratio of stableisotopes of a constituent element can be used as a substance forisotopic labels. A dye can be synthesized for use as a substance for anisotopic label by controlling the content ratio or ratios of stableisotopes of one or more constituent elements of raw materials. Byselecting the type and structural position of an element, amongconstituent elements of raw materials, which is controlled in thecontent ratio of stable isotopes thereof, there can be synthesized a dyewhich is equal to an ordinarily prepared dye with respect to theabsorption, reflection and transmission characteristics in the visibleregion but differs therefrom with respect to the vibration spectrum inthe infrared region. This enables one to realize a isotopic labelconstituting substance which cannot be distinguished from ordinary dyesthrough visual judgment but can be judged for the first time as anisotopic label constituting substance upon measurement of absorption,reflection or transmission characteristics within a specific wave lengthregion (wave number region) and is thus high in security level.

Specific Example 1 of a Dye Substance for Isotopic Label: Phthalocyanine

This is a substance which is obtained by heating phthalic anhydride (orphthalimide) and a metal salt in urea melt. When the content ratio ofstable isotopes of carbon C, nitrogen N or hydrogen H which is aconstituent element of starting urea or phthalic anhydride (orphthalimide) is controlled, the content ratio of the stable isotopes ofthe constituent element in the resulting phthalocyanine can becontrolled. When a copper salt is used as the metal salt, a blue dye isobtained, and when a chlorine atom is arranged at the benzene ring, agreen dye is obtained.

Specific Example 2 of a Dye Substance for Isotopic Label: Indigo

This is a blue dye. After addition of formaldehyde and sodium cyanide(or potassium cyanide) to aniline, sodium hydroxide is added to, therebypreparing N-phenylglycine, followed by dehydration reaction to prepareindoxyl. This is oxidized in an alkaline solution or oxidized in air toobtain indigo. When the content ratio of stable isotopes of carbon C,nitrogen N, oxygen O or hydrogen H, which is a constituent element ofstarting aniline, formaldehyde, sodium cyanide (potassium cyanide) orsodium hydroxide, is controlled, the stable isotope content ratio of theconstituent element of the synthesized indigo can be controlled.

Specific Example 3 of a Dye Substance for Isotopic Label: Aniline Black

This is a black dye obtained by oxidative condensation of aniline. Anaqueous solution of aniline hydrochloride and an oxidizing agent(dichromic acid or sodium chlorate) is heated to cause an oxidationcondensation reaction. When the stable isotope content ratio of carbonC, nitrogen N or hydrogen H which is a constituent element of thestarting aniline is controlled, the stable isotope content ratio of theconstituent element of the resulting aniline black can be controlled.

Specific Example 4 of a Dye Substance for Isotopic Label: Magenta

This is a reddish purple dye obtained by oxidative condensation ofhydrochloride compounds of aniline, p-toluidine and o-toluidine withnitrobenzene. When the stable isotope content ratio of carbon C,nitrogen N or hydrogen H which is a constituent element of the startinghydrochloride compounds of aniline, p-toluidine and o-toluidine iscontrolled, the stable isotope content ratio of the constituent elementof the resulting magenta can be controlled.

Specific Example 5 of a Dye Substance for Isotopic Label: Methyl Violet

This is a bluish purple dye prepared by heating a mixture ofdimethylaniline, phenol, copper sulfate, sodium chloride and water foroxidative condensation of the dimethyl aniline via air. When the stableisotope content ratio of carbon C, nitrogen N or hydrogen H which is aconstituent element of the starting dimethylaniline or phenol iscontrolled, the stable isotope content ratio of the constituent elementof the resulting methyl violet can be controlled.

Specific Example 6 of a Dye Substance for Isotopic Label: Azo Methine

This is a yellow dye prepared by heating, for condensation, an anilinederivative (such as aminoaniline or the like) and an aldehyde derivative(nitrobenzaldehyde or the like) in an alcohol in the presence of a smallamount of an acid. When the stable isotope content ratio of carbon C,nitrogen N, oxygen O or hydrogen H which is a constituent element of thestarting aniline derivative or aldehyde derivative is controlled, thestable isotope content ratio of the constituent element of the resultingazo methine can be controlled.

Specific Example 7 of a Dye Substance for Isotopic Label: Quinacridone

Aniline and diethyl-2,5-hydroxy-1,4-cyclohexadiene-1,4-dicarboxylate areprovided as starting material to obtain a red dye through intramolecularring-closing reaction. When the content ratio of stable isotopes ofcarbon C, nitrogen N, oxygen O or hydrogen H serving as a constituentelement of the starting materials is controlled, the content ratio ofthe stable isotopes of the constituent element in the resultantquinacridone can be controlled.

Example 7

This example is one wherein the vibration spectrum of an isotopic labelis read to judge the authenticity of an article attached with theisotopic label based on the results of the reading. The system used inthe present invention includes, for instance, a device for reading andobtaining a vibration spectrum, a device for reading an isotopic labelby subjecting the data of the vibration spectrum to pattern recognition,and a device for judging the authenticity of an article throughinformation of the isotopic label.

The respective devices may be not only those which are set at oneposition, but also those wherein one or plural devices are separatelylocated and mutually connected with one another through a communicationnetwork. The communication network includes, aside from a telephonecommunication network, at least one of an internet and an intranet. Thisensures not only individual devices being not limited with respect tothe installation location and the geographical site, but also thepossibility of control from a remote area or the designation of controlparameters from a remote area. For instance, using a control device at aremote area, the operations of the respective devices including thedesignation of an isotopic label attaching position where data is to beobtained by a vibration spectrum measuring device, the selection of ajudgment model used in an isotopic label reading device, the judgmentlogic of a device of judging authenticity and the like may be altered orrenewed depending on the circumstances, if necessary, while working thesystem.

FIG. 12 is an application of the invention to a card verifier using acommunication network. In order that one opens the door from outside ofa building and enters into the building, a card (ID card) attached withan isotopic label has to be inserted into a vibration spectrum obtainingdevice (i.e. an external verifier). This permits data to be obtainedwith respect to the vibration spectrum of the isotopic labelconstituting substance attached to the card, time and the like. Next,these data are transferred to an isotopic label reading device (aninside server) via an intranet and subjected to pattern recognition forreading as an isotopic label. For instance, the isotopic label attachedto the card reveals that the person inserting the card may be recognizedas an employee belonging to the department in the building, an employeein other department, an employee of a related company, VIP, a person onthe blacklist or the like. The results of the recognition aretransferred to an authenticity judging device (i.e. a server of a headoffice) via an internet thereby judging the authenticity of the insertedcard.

If the card is judged as true, instructions are issued via the internetso as to execute the preset operations for every result of recognition.For instance, where recognized as an employee belonging to thedepartment in the building, the door is unlocked, and where recognizedas an employee of a related company, VIP or a person on the blacklist, apredetermined message is sent to a preliminarily designated person incharge simultaneously with the door being unlocked. On the other hand,when judged as false, no unlocking instruction is issued on the door. Inthis case, it is possible to preliminarily designate the option that thewarning buzzer set near the door is on.

A series of control parameters including the position of attaching anisotopic label to be read can be designated by transfer from a controlterminal to a vibration spectrum obtaining device via an internal line.This function becomes necessary in case where a plurality of isotopiclabels are attached to an ID card for improving a security level. A moreelaborated judging model is developed while taking into account theexisting circumstances of forgery and is transferred to the isotopiclabel reader via an internal line to update a discrimination model.

The isotopic label discrimination system set forth hereinabove can beapplied to a method of nondestructively judging the authenticity of anarticle. More particularly, because a substance constituting theisotopic label has an inherent vibration spectrum which does notordinarily exist in a natural field, it is possible to determine whetheror not an article is true or false in high precision depending on theconformity or inconformity with the vibration spectrum. The detectingmethod, valuation conditions and judging conditions can besimultaneously set from outside through a communication, so thatmaintenance is simpler than that of an existing ROM type and the effectof preventing the leakage of determination standards is higher.

Moreover, the results of the judgment obtained in the above-statedevaluation data extraction mechanism, comparison mechanism withreference data, and results-judging mechanism can be stored in a memoryalong with additional data such as of days, times, and places, and thuscan be used in various controls of articles on which an isotopic labelhas been attached. For instance, a substance for an isotopic label, acontrol number and the like are recorded, and the results of judgmentare logged and stored in the memory of the isotopic label judging systemalong with the additional data such as of days and times and places.This leads to the discovery of the existence of a counterfeit other thanthe authentic by detecting the unnatural situation of tacking data ofdays, times and places, or the fact of alternate judgment, for example,in Hokkaido or Okinawa even if the results of judgment are same orarticles are forged perfectly.

EFFECTS OF THE INVENTION

According to the invention, information of an isotopic label attached onan article beforehand can be read readily and quickly withoutdestruction. Further, according to the invention, various excellenteffects can be obtained including the judgment of authenticity of anarticle being made nondestructively and in high precision based on theobtained information. The isotopic label per se for nondestructivereading according to the invention is difficult to forge and falsify, sothat the purpose of anti-counterfeiting or the like can be achievedreliably in high precision.

1. A method for nondestructive reading of an isotopic label on anarticle comprising a) the isotopic label made of substances which,respectively, have at least one constituent element having a pluralityof stable isotopes and which include both a substance wherein a contentratio of at least one stable isotope of the constituent element is nothigher than a natural isotopic abundance ratio, and another substancewherein a content ratio of the same stable isotope is not lower than thenatural isotopic abundance ratio, and said substances having a vibrationspectrum different from the vibration spectrum of the substance whereinall content ratios of the stable isotopes of the constituent elementsare equal to the natural isotopic abundance ratios, respectively, b)attaching the isotopic label on the article beforehand, and c) obtainingthe vibration spectrum of the substances for the isotopic labelnondestructively.
 2. A method for nondestructive reading of an isotopiclabel on an article comprising a) the isotopic label made of a substancewhich has at least two elements selected from hydrogen, carbon, nitrogenand oxygen with each of the content ratios of stable isotopes thereofcontrolled to be different from the natural isotopic abundance ratio andwhich has a vibration spectrum different from the vibration spectrum ofthe substance whose content ratios of stable isotopes of the constituentelements are, respectively, equal to the natural isotopic abundanceratios, b) attaching the isotopic label on the article beforehand, andc) obtaining the vibration spectrum of the substance for the isotopiclabel nondestructively.
 3. A method for nondestructive reading of anisotopic label on an article comprising a) the isotopic label made of asubstance, which has at least two elements selected from hydrogen,carbon, nitrogen and oxygen with each of the content ratios of stableisotopes thereof controlled to be different from the natural isotopicabundance ratio, which has a vibration spectrum different from thevibration spectrum of the substance whose content ratios of stableisotopes of the constituent elements are, respectively, equal to thenatural isotopic abundance ratios, and wherein the constituent elementsother than hydrogen, carbon, nitrogen and oxygen have no stableisotopes, b) attaching the isotopic label on the article beforehand, andc) obtaining the vibration spectrum of the substance for the isotopiclabel nondestructively.
 4. A method for nondestructive reading of anisotopic label on an article according to claim 1, characterized in thatthe vibration spectrum of the substance or substances for said isotopiclabel is nondestructively obtained by an infrared absorption method. 5.A method for nondestructive reading of an isotopic label on an articleaccording to claim 1, characterized in that the vibration spectrum ofthe substance or substances for said isotopic label is nondestructivelyobtained by an infrared absorption method and obtained by an attenuatedtotal reflectance method.
 6. A method for nondestructive reading of anisotopic label on an article according to claim 1, characterized in thatthe vibration spectrum of the substance or substances for said isotopiclabel is nondestructively obtained by an infrared absorption method andobtained by a diffuse reflection method.
 7. A method for nondestructivereading of an isotopic label on an article according to claim 1,characterized in that the vibration spectrum of the substance orsubstances for said isotopic label is nondestructively obtained by useof an acousto-optical tunable filter.
 8. A method for nondestructivereading of an isotopic label on an article according to claim 1,characterized in that the vibration spectrum of the substance orsubstances for said isotopic label is nondestructively obtained by aRaman scattering method.
 9. A method for nondestructive reading of anisotopic label on an article according to claim 8, characterized in thatthe vibration spectrum nondestructively obtained by the Raman scatteringmethod is a vibration spectrum obtained by use of a semiconductor laseras a laser beam source, and the isotopic label is identified by using,in combination, information of a light absorption spectrum obtained byuse of the light with at least three kinds of wavelengths generated bysaid semiconductor laser.
 10. A method for nondestructive reading of anisotopic label on an article according to claim 1, characterized in thatthe vibration spectrum of the substance or substances for said isotopiclabel is nondestructively obtained by means of light with at least threekinds of wavelengths generated by a semiconductor laser.
 11. A methodfor nondestructive reading of an isotopic label on an article accordingto claim 10, characterized in that the vibration spectrum of thesubstance for said isotopic label is a vibration spectrum obtained byuse of the light with at least three kinds of wavelengths generated by asemiconductor laser, which is used in combination of information oflight absorption spectra obtained by use of the light with at leastthree kinds of wavelengths generated by another semiconductor laser. 12.A method for nondestructive reading of an isotopic label on an articleaccording to claim 1, characterized in that data of the vibrationspectrum obtained by the nondestructive method of said isotopic labelare identified by subjecting to pattern recognition by use of adiscrimination model made according to a multi-variate analysis inchemometrics.
 13. A method for nondestructively judging authenticity ofan article attached with an isotopic label thereon by use of anondestructive reading method comprising a) the isotopic label made ofsubstances which, respectively, have at least one constituent elementhaving a plurality of stable isotopes and which include both a substancewherein a content ratio of at least one stable isotope of theconstituent element is not higher than the natural isotopic abundanceratio, and another substance wherein a content ratio of the same stableisotope is not lower than the natural isotopic abundance ratio, and saidsubstances having a vibration spectrum different from the vibrationspectrum of the substance wherein all content ratios of the stableisotopes of the constituent elements are equal to the natural isotopicabundance ratios, respectively, b) attaching the isotopic label on thearticle beforehand, c) obtaining the vibration spectrum of thesubstances for the isotopic label nondestructively, and d) judging theauthenticity of said article based on the thus obtained information. 14.A method for nondestructively judging authenticity of an articleattached with an isotopic label thereon comprising a) the isotopic labelmade of a substance which has at least two elements selected fromhydrogen, carbon, nitrogen and oxygen with each of the content ratios ofstable isotopes thereof controlled to be different from the naturalisotopic abundance ratio and which has a vibration spectrum differentfrom the vibration spectrum of the substance whose content ratios ofstable isotopes of the constituent elements are, respectively, equal tothe natural isotopic abundance ratios, b) attaching the isotopic labelon the article beforehand, c) obtaining the vibration spectrum of thesubstance for the isotopic label, and d)judging the authenticity of saidarticle based on the thus obtained information.
 15. A method fornondestructively judging authenticity of an article attached with anisotopic label thereon comprising a) the isotopic label made of asubstance, which has at least two elements selected from hydrogen,carbon, nitrogen and oxygen with each of the content ratios of stableisotopes thereof controlled to be different from the natural isotopicabundance ratio, which has a vibration spectrum different from thevibration spectrum of the substance whose content ratios of stableisotopes of the constituent elements are, respectively, equal to thenatural isotopic abundance ratios, and wherein the constituent elementsother than hydrogen, carbon, nitrogen and oxygen have no stableisotopes, b) attaching the isotopic label on the article, c) obtainingthe vibration spectrum of the substance for the isotopic labelnondestructively, and d) judging authenticity of said article based onthe thus obtained information.
 16. A method for nondestructively judgingauthenticity of an article attached with an isotopic label thereonaccording to claim 13, characterized in that a vibration spectrumobtaining device, a device for reading information of the isotopic labelby subjecting data of the vibration spectrum to pattern recognition anda device for judging authenticity of the articles are worked byconnection via a communication network.
 17. A method fornondestructively judging authenticity of an article attached with anisotopic label thereon according to claim 16, characterized in that saidcommunication network includes at least one of a telephone communicationnetwork, an internet and an intranet.
 18. A method for nondestructivelyjudging authenticity of an article attached with an isotopic labelthereon according to claim 16, characterized in that at least one ofsaid vibration spectrum obtaining device, said device for readinginformation of the isotopic label by subjecting data of the vibrationspectrum to pattern recognition and said device for judging authenticityof the article is controlled from a remote area or is designated withcontrol parameters from a remote area.
 19. An isotopic label fornondestructive reading which is attached on an article beforehandcomprising substances constituting said isotopic label which,respectively, have at least one constituent element having a pluralityof stable isotopes and which include both a substance wherein a contentratio of at least one stable isotope of the constituent element is nothigher than a natural isotopic abundance and ratio and another substancewherein a content ratio of the same stable isotope is not lower than thenatural isotopic abundance ratio, and said substances having a vibrationspectrum different from the vibration spectrum of the substance whereinall content ratios of the stable isotopes of the constituent elementsare equal to the natural isotopic abundance ratios, respectively.
 20. Anisotopic label for nondestructive reading which is attached on anarticle beforehand comprising a substance constituting said isotopiclabel which has at least two elements selected from hydrogen, carbon,nitrogen and oxygen with each of the content ratios of stable isotopesthereof being controlled to be different from the natural isotopicabundance ratio, and which has a vibration spectrum different from thevibration spectrum of the substance whose content ratios of stableisotopes of the constituent elements are equal to the natural isotopicabundance ratios, respectively.
 21. An isotopic label for nondestructivereading which is attached on an article beforehand comprising asubstance constituting said isotopic label which has at least twoelements selected from hydrogen, carbon, nitrogen and oxygen with eachof the content ratios of stable isotopes thereof being controlled to bedifferent from the natural isotopic abundance ratio, which has avibration spectrum different from the vibration spectrum of thesubstance whose content ratios of stable isotopes of the constituentelements are, respectively, equal to the natural isotopic abundanceratios, and wherein the constituent elements of said substance otherthan hydrogen, carbon, nitrogen and oxygen have no stable isotopes. 22.An isotopic label for nondestructive reading which is attached on anarticle beforehand according to claim 19, characterized in that thevibration spectrum of the substance for said isotopic label contains atleast one M-shaped or W-shaped pattern, in which adjacent two peaks arepartially superposed, at a portion different from the vibration spectrumof the substance having the content ratio or ratios of stable isotopesof the constituent elements equal to the natural isotopic abundanceratio or ratios, respectively.
 23. An isotopic label for nondestructivereading according to claim 19, characterized in that said isotopic labelhas a form in which the substance or substances controlled in the stableisotope ratio of the constituent element or elements are attached to twoor more places.
 24. An isotopic label for nondestructive readingaccording to claim 19, characterized in that said isotopic label has aplurality of portions attached with the substance or substancescontrolled in the stable isotope ratio or ratios of the constituentelement or elements and said substance or substances is arrangedtwo-dimensionally.
 25. An isotopic label for nondestructive readingaccording to claim 19, characterized in that the substance for saidisotopic label consists of urea, glycine, leucine, alanine, glucose,ammonium nitrate, ammonium acetate, ammonium phosphate, sodiumphosphate, benzamide, sodium nitrate, diphenyl, dicyclohexane, benzoicacid, sodium acetate, sodium carbonate, sodium hydrogen carbonate,sodium propionate, sodium formate, sodium octoate, sodium glutamate,phthalimide, valine, sodium octanoate, or sodium palmitate.
 26. Anisotopic label for nondestructive reading according to claim 19,characterized in that the substance for said isotopic label consists ofa dye.
 27. An isotopic label for nondestructive reading according toclaim 19, characterized in that the substance for said isotopic labelconsists of a dye whose light absorption spectrum in the visible regionis equal to the light absorption spectrum of the dye having contentratios of stable isotopes of the elements constituting thelast-mentioned dye equal to the natural isotopic abundance ratios,respectively, and whose vibration spectrum in the infrared regiondiffers from the vibration spectrum of the dye having content ratios ofstable isotopes of the elements constituting the last-mentioned dyeequal to the natural isotopic abundance ratios, respectively.
 28. Anisotopic label for nondestructive reading according to claim 19,characterized in that the substance for said isotopic label is a dyeselected from phthalocyanine, indigo, aniline black, magenta, methylviolet, azo methine, and quinacridone.